It is possible to produce irregular structures quickly and accurately using rapid prototyping technology. However, there are still some obstacles in fabricating large-scale structures. In order to overcome these technical hitches, equipment has been developed for manufacturing irregular structures using EPS, making it an easy process. Conventional laser cutting systems can produce undesirable slopes in the structure when cutting EPS due to the divergence of the laser beam, resulting in step differences in the overall shape. Therefore, the objective of this study was to reduce the divergence of the laser beam using a concave lens and to find the optimal cutting conditions of the EPS through cutting experiments. As a result of the study, it was confirmed that the collimated beam cutting system can reduce the cutting slopes compared to the focused beam cutting system. In addition, experimental equations for depth of cut with cutting speed and laser intensity were derived.